It has been common practice for sometime in the truck rental industry to supply a ramp with the truck to facilitate loading and unloading the truck. A significant advance was made in this art when the inventors recognized the possibility of providing a storage space for the ramp beneath the truck floor between the longitudinal frame members of the truck chassis.
Storage of the ramp in the frame of the truck offers several advantages. Such storage is outside the body of the truck and therefore does not occupy valuable cargo space nor interfere with articles stored in the truck body. Furthermore, this storage arrangement positions the ramp at the rear of the truck immediately beneath the floor of the truck body where it is accessible to the user who merely needs to withdraw the ramp from its storage space and place it in use.
Representative prior art arrangements for frame storage of ramps are disclosed in a series of three U.S. Patents granted to John C. Abromavage and Henry S. Shattles, namely: U.S. Pat. Nos. 3,511,393 granted May 12, 1970 for "RAMP ASSEMBLY"; No. 3,559,826 granted Feb. 2, 1971 for "AUTOMOTIVE CHASSIS"; and 3,713,662 granted Jan. 30, 1973 for "CHASSIS WITH STORAGE SPACE".
All of the aforementioned Abromavage et al patents disclose releasable latches for locking the ramp in its stored position to prevent accidental dislodgement of the ramp when the truck is moved. There are no provisions, however, for locking the latches themselves. Consequently, with the arrangements of the '826 and '662 patents the ramps are exposed to theft when the truck is left unattended. In the '393 patent a rather elaborate and costly set of pivoted arms prevent the ramp from becoming completely detached from the truck.
Theft of loading ramps has become a major problem for truck rental fleets. For ease of handling such ramps are usually made of aluminum which has considerable scrap metal value and encourages theft.
Now, it has long been the practice to provide a lockable latch for the access door of rental trucks. U.S. Pat. No. 3,740,978 granted June 26, 1973 to Vernon O. Smith et al for "LATCH AND LOCK STRUCTURE" discloses such a latch.
So far as is known, however, the door latch lock has not been employed to secure and prevent theft of a loading ramp aside from locking the ramp inside the cargo space. And the latter expedient uses valuable cargo space.